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In 8 normotensive subjects and in 8 patients with essential hypertension total catecholamine content and dopamine-beta-hydroxylase (DBH) activity in plasma were measured at rest and during physical exercise. Catecholamine levels at rest were significantly higher in the hypertensive than in the normotensive persons whereas the 2 groups of subjects did not differ in DBH activity at rest. At a work load of 150 watts there was a more pronounced increase of the catecholamine concentrations and of the DBH activity in the hypertensive patients than in the normotensives. One may conclude from the data that there is an increased sympathetic nerve activity in patients with essential hypertension.

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Changes in tissue levels of cyclic adenosine 3’:5’-monophosphate (cAMP) and cyclic guanosine 3’:5’-monophosphate (cGMP) in the rat kidney in response to acid-base changes and administration of acetazolamide were measured. cAMP was determined according to the method described by Gilman and cGMP by radioimmunoassay. 1 mg/kg acetazolamide increased bicarbonate excretion 100-fold over the control values to 2.52 ± 0.5 mEq/min (mean ± SEM; n = 6), but did not influence cGMP and cAMP tissue content. 10 and 100 mg/kg acetazolamide increased cGMP tissue levels to 0.277 ± 0.048 and 0.482 ± 0.07 pmol/mg dry weight in comparison to 0.192 ± 0.04 in the controls, whereas no changes in cAMP levels occurred. Chronic as well as acute metabolic alkalosis induced an increase of cGMP levels (0.26 ± 0.03 and 0.29 ± 0.06 pmol/mg), whereas chronic metabolic and acute respiratory acidosis lowered cGMP levels to 0.14 ± 0.02 and 0.13 ± 0.02 pmol/mg. cAMP tissue levels were not affected by changes in acid-base balance. The data could suggest that cGMP participates in the regulation of acid-base balance and renal effects of acetazolamide.

No abstract